Kelly-Anne Kidston
In this experiment we shall use a 125-mL Erlenmeyer flask in place of the glass bulb used by Dumas 🤓 A small sample of an unknown volatile liquid will be placed in the flask and the liquid vaporized by immersing the flask in a hot water bath 🙈 To seal the flask, a piece of aluminum foil is used. A tiny hole in the foil allows excess vapor to escape. By measuring the temperature of your gas, you can determine the temperature. Water bath Assuming that there is thermal equilibrium between the gas and water baths, place the flask around the tank. The volume of vapor that is produced by the liquid from excess liquids is higher than the volume in the flask because it is not used enough. The liquid vaporizes upon heating. Vapor that is created initially pushes the air out of the flask and then the vapor begins exiting the flask through the pinhole until the pressure The atmospheric pressure inside the flask equals the internal pressure. You can determine the pressure by using a barometer in the laboratory to measure the atmosphere pressure. The flask should be removed from the hot bath after the last drop of liquid has evaporated. After cooling, the vapor in the flask can condense and cool down. You can measure the mass of the remaining condensate in the flask by measuring its weight. The volume of the condensate is equal to that of the flask. Weighing the flask and filling it with deionized liquid will determine its volume. Then, we’ll measure the temperature. We can calculate the water’s volume by measuring its mass and the density at the temperature we are using. To determine the molecular mass average of an unknown liquid, three trials are required. Below is a table showing the densities for water at different temperatures. [1]
2 The method for determining the relative molecular weights of volatile liquids using weighing. It’s is making of thin glass with a narrow neck and a very long neck. It is fully weighed. Air at known temperatureAfter that, a tiny amount of the sample is added to the bulb and it is then heated (in an oven) until the liquid is vaporized. The air is removed. After sealing the tip of the neck, the bulb is cooled to room temperature and then weighed. You can find the volume by adding water to it and then weighing it again. Calculating the volume of vapour can be done if you know the density. We are grateful to Nikeshia Barney, Ibb (Yemen), for sharing this information with us. [2]
Researchers from web.lemoyne.edu Additional information is available. Notes Jean-Baptiste Dumas (1860-1884) developed a method to calculate the molar mass for substances which could be easily converted into vapors. It is still used in laboratory exercises for chemistry students. The Dumas method involves the determination of the mass, volume temperature and pressure of a substance during its vapor phase. Modern Dumas methods use the ideal gas law to determine the molar mass. This is how the experiments are done. Dumas did not develop the concept of the’s Mole. On the basis of relative gas density, Dumas computed the molar masses or rather relative molecular mass. The ratio of a vapor to hydrogen is equal to its density multiplied by hydrogen’s under similar conditions. This method is based on Avogadro’s hypothesis that similar gases contain equal numbers of molecules. Dumas knew how to modify a measured density to indicate a change in pressure, namely using Boyle’s law. He also knows how adjust the temperature using Charles’ law. We are grateful to Kiernan Hand who shared this information with us. [3]
Notes Jean-Baptiste Dumas (1860-1884) developed a method to calculate the molar mass for substances, which could be easily converted into vapors. It is still used in laboratory exercises for chemistry students. The Dumas method involves the determination of the mass, volume temperature and pressure of a substance during its vapor phase. Modern Dumas methods use the ideal gas law to determine the molar mass. This is how the experiments are done. Dumas was not the first to develop the notion of “the’s mole”. On the basis of relative gas density, Dumas computed the molar masses or rather relative molecular mass. A vapor’s molar mass relative to hydrogen was equal to its density divided by the hydrogen in comparable circumstances. This method is based on Avogadro’s hypothesis that similar gases contain equal numbers of molecules. Dumas knew how to modify a measured density to indicate a change in pressure using Boyle’s law, and Charles knows how adjust the temperature using Charles’ law. [4]
Use a utility clamp attached to a Erlenmeyer flask measuring 125 mL. Put it into a 600 mL saucepan. You can pour water around the flask’s outside until it is nearly full. Allow room to simmer. You must ensure that the water does not get into your flask. Add a few boiling chips and the flask to the water. Heat the water Bring the mixture to a boil over a Bunsen-burner. Remove the clamp from your flask while the water heats and allow it to dry thoroughly. Paper towel. A small piece of aluminum foil should be placed over the mouth. The foil should be folded around the flask’s neck. Use a rubber band to hold the foil in place. A straight pin can be used to make a tiny hole in the middle of the foil. Make sure the hole is not blocked partially by aluminum foil. The flask, rubber band, and foil cap should be weighed to within a milligram. Gini Egan’s revisions are greatly appreciated. [5]
Article references
- https://chem.libretexts.org/Ancillary_Materials/Laboratory_Experiments/Wet_Lab_Experiments/General_Chemistry_Labs/Online_Chemistry_Lab_Manual/Chem_11_Experiments/11B:_The_Dumas_Method_(Experiment)
- https://www.oxfordreference.com/view/10.1093/oi/authority.20110803095734274
- https://web.lemoyne.edu/giunta/classicalcs/dumasnote.html
- https://web.lemoyne.edu/~giunta/classicalcs/dumasnote.html
- http://intro.chem.okstate.edu/HTML/SEXP8.HTM
